PHOTOOXIDATION PRODUCTS OF MEROCYANINE 540 FORMED UNDER PREACTIVATION CONDITIONS FOR TUMOR THERAPY

In order to gain insight into the preactivation of merocyanine 540 (MC540) 1 for the photodynamic therapy (Gulliya et al., 1990a, Photochem. Photobiol. 52, 831-838) its photo-oxidation was investigated. After irradiation of MC540 1 on a preparative scale three main photodegradation products were isolated with 16-20% yields. They turned out to be derivatives of benzoxazole, thiouracil and thiohydantoin with the structures 4, 5 and 6, respectively. It may be possible that they contribute to the cytostatic and antiviral activity of preactivated MC540 1.     

Eine ganze Funktion,für die jede komplexe Zahl Konvergenzwert ist

Ohne Zusammenfassung     

Hydrogen dissociation on metal surfaces – a model system for reactions on surfaces

Received: 23 March 1998/Accepted: 21 August 1998     

STRUCTURE OF METHYLPHEOPHORBIDE-RCI*

Abstract— The methanolic extract of the cyanobacterium (blue-green alga) Spirulina geitleri has been treated with methanolic acid to convert all chlorophyllous pigments to their methylpheophorbides. Fractionation of the latter from methylpheophorbide a by thin layer chromatography and high pressure liquid chromatography yielded methylpheophorbide-RCI. Its structure has been determined as 13²S-hydroxy-20-chloro-methylpheophorbide a by ¹H-nuclear magnetic resonance, absorption and circular dichroism spectroscopy, mass spectrometry and by partial synthesis from chlorophyll a. The pigment is isolated from Spirulina geitleri irrespective of the use or omission of chlorinated substances during the isolation procedure.     

Clean-up of some organochlorine and pyrethroid insecticides by automated solid-phase extraction cartridges coupled to capillary GC-ECD

The ASPEC (Automatic Sample Preparation with Extraction Columns) system has been coupled on-line to capillary GC-ECD by means of a loop-type interface equipped with a solvent vapour exit. Both ASPEC and GC conditions have been optimized leading to an effective clean-up of the extracts analyzed. By means of solid-phase extraction cartridges filled with silica, it has been possible to analyze concentrated surface water extracts for a group of 18 electron-capturing compounds present in the water at ppt levels. ASPEC-GC has also been applied to the determination of synthetic pyrethroids at ppt levels in surface water. The complete analytical procedure is greatly facilitated by automation and miniaturization. Miniaturization results in a considerable decrease in the sample volume required. The potential of the method for the analysis of other pesticides is estimated.     

The derivatization of fatty acids by (chloro)alkyl chloroformates in non-aqueous and aqueous media for GC analysis

Fatty acids can be conveniently derivatized in less than one minute with (chloro)alkyl chloroformates such as methyl chloroformate, 2-chloroethyl chloroformate and 2,2,2-trichloroethyl chloroformate. 2,2,2-Trichloroethyl chloroformate is the most reactive reagent, and yields a reaction product which can be sensitively detected by GC ECD (detection limit 50 ng/ml, i.e. 25 pg/injection, for C⁸, C¹⁰, and C¹² acids). In non-aqueous media 3-picoline, N-methylpiperidine, and dimethylaminopyridine show catalytic activity comparable with that of pyridine and can, therefore, replace it. N-methylpiperidine is the best basic catalyst in aqueous media (i.e. media containing up to 40 % water).